An impact crusher for crushing material of various consistencies is known for example from DE 23 31 729 A1 in which the impact plates are interconnected in articulated manner to form a coherent composite pivotal impact member, each of the interconnected impact plates deriving adjustable support individually from the housing.
The impact plates may have impact surfaces which are at angles to one another or are stepped along the path of the material as it is entrained from the inlet side of the machine. The principles of such machines have also been developed in the Chemical Engineers Handbook, Perry and Chilton, 5th edition, McGraw Hill Book Company, New York, 1973, at Chapter 8, pages 19 ff.
This known impact crusher, just like impact other crushers of the same genus, suffers from the substantial drawback that the upper impact member, provided downstream of the machine inlet yields outwardly due to foreign objects which cannot be crushed entering the machine, so that the crushing gap between the rotor and the lower impact member is decreased to such an extent, due to the upper impact member pivoting outwardly, that a risk arises of foreign objects getting wedged between the rotor and the impact member, leading to possible damage to the rotor and/or the impact member, so that the continued operability of the installation can no longer be ensured.